Starship Asterisk*

neufer wrote: ↑Wed Oct 31, 2018 7:20 pm

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Ann wrote: ↑Wed Oct 31, 2018 6:18 pm

BillT wrote: ↑Wed Oct 31, 2018 10:33 am
The carbon star DY Crucis is interesting to observe in contrast to the adjacent 1st magnitude Beta Crucis (Mimosa). The two are separated by only a bit over two arc minutes. There is a big difference in brightness but that seems to enhance the deep red colour of DY Crucis.

The juxtaposition of Beta Crucis and DY Crucis should really enhance the deep red color of DY Cru, but it seems to me that it should also help bring out the blue color of Beta Crucis. Beta Cru is really quite blue, with one of the most negative B-V indexes in the sky, at least among the bright stars.

https://en.wikipedia.org/wiki/Mimosa wrote:
<<Mimosa is a genus of about 400 species of herbs and shrubs, in the mimosoid clade of the legume family Fabaceae. The generic name is derived from the Greek word μιμος (mimos), an "actor" or "mime," and the feminine suffix –osa, "resembling", suggesting its 'sensitive leaves' which seem to 'mimic conscious life'. Members of this genus are among the few plants capable of rapid movement; examples outside of Mimosa include the telegraph plant, Aldrovanda, some species of Drosera and the famous venus flytrap. The leaves of the Mimosa pudica close quickly when touched. Some mimosas raise their leaves in the day and lower them at night, and experiments done by Jacques d'Ortous de Mairan on mimosas in 1729 provided the first evidence of biological clocks. Note that, botanically, what appears to be a single globular flower is actually a cluster of many individual ones. Mimosa contains some level of heptanoic acid [an oily liquid that contributes to the odor of some rancid oils.].

A mimosa cocktail is composed of one part champagne (or other sparkling wine) and one part chilled citrus juice, usually orange juice unless otherwise specified.>>

BillT wrote: ↑Wed Oct 31, 2018 10:33 am The carbon star DY Crucis is interesting to observe in contrast to the adjacent 1st magnitude Beta Crucis (Mimosa). The two are separated by only a bit over two arc minutes. There is a big difference in brightness but that seems to enhance the deep red colour of DY Crucis.

neufer wrote: ↑Wed Oct 31, 2018 2:18 pm

BDanielMayfield wrote: ↑Wed Oct 31, 2018 2:00 pm
Ah, "helium fusion". Gota love the triple alpha process.

No carbon (nor any heavier elements either, pretty much) without it.

• We exist "according to Hoyle"

https://en.wikipedia.org/wiki/Carbon-12#Hoyle_state wrote:
<<The Hoyle state is an excited, spinless, resonant state of carbon-12. It is produced via the triple-alpha process, and was predicted to exist by Fred Hoyle in 1954. The existence of the Hoyle state is essential for the nucleosynthesis of carbon in helium-burning red giant stars, and predicts an amount of carbon production in a stellar environment which matches observations. The existence of the Hoyle state has been confirmed experimentally, but its precise properties are still being investigated. In 2011, an ab initio calculation of the low-lying states of carbon-12 found (in addition to the ground and excited spin-2 state) a resonance with all of the properties of the Hoyle state.>>

8Be has a very short half-life of about 7×10−17 s that contributes to its significant cosmological role, as elements heavier than beryllium could not have been produced by nuclear fusion in the Big Bang.[14] This is due to the lack of sufficient time during the Big Bang's nucleosynthesis phase to produce carbon by the fusion of 4He nuclei and the very low concentrations of available beryllium-8. The British astronomer Sir Fred Hoyle first showed that the energy levels of 8Be and 12C allow carbon production by the so-called triple-alpha process in helium-fueled stars where more nucleosynthesis time is available. This process allows carbon to be produced in stars, but not in the Big Bang. Star-created carbon (the basis of carbon-based life) is thus a component in the elements in the gas and dust ejected by AGB stars and supernovae (see also Big Bang nucleosynthesis), as well as the creation of all other elements with atomic numbers larger than that of carbon.

BDanielMayfield wrote: ↑Wed Oct 31, 2018 2:00 pm
Ah, "helium fusion". Gota love the triple alpha process.

No carbon (nor any heavier elements either, pretty much) without it.

• We exist "according to Hoyle"

https://en.wikipedia.org/wiki/Carbon-12#Hoyle_state wrote:
<<The Hoyle state is an excited, spinless, resonant state of carbon-12. It is produced via the triple-alpha process, and was predicted to exist by Fred Hoyle in 1954. The existence of the Hoyle state is essential for the nucleosynthesis of carbon in helium-burning red giant stars, and predicts an amount of carbon production in a stellar environment which matches observations. The existence of the Hoyle state has been confirmed experimentally, but its precise properties are still being investigated. In 2011, an ab initio calculation of the low-lying states of carbon-12 found (in addition to the ground and excited spin-2 state) a resonance with all of the properties of the Hoyle state.>>

distefanom wrote: ↑Wed Oct 31, 2018 6:58 am I wonder, how would be the sky color on a hypothetical hearth-like planet, orbiting around such a star...